1. Field Of The Invention
The present invention relates to an underwater sonar tracking system and more particularly relates to an acoustic transponder that can be deployed in multiple positions for example along an underwater cable as used in seismic work. Even more particularly, the present invention relates to an underwater transponder that can be installed in an underwater array wherein an improved battery powered transponder uses a removable battery pack that plugs into an electronics module with a water displacing connection, both the battery pack and electronics package being disposable, self-contained and connectable structures that can be changed in a wet environment.
2. General Background
In seismic exploration, there is often employed an underwater array of acoustic transponders or slave transponders. A master transceiver unit is located on a survey vessel. Because of range limitations, it is often necessary to employ a very large quantity of cable transponders. Sometimes in very shallow water operation or in the use of "bay cables" and in R. F. telemetry buoy systems, acoustic ranges can be very short.
Slave transponders and the master transceiver unit often have to operate in high reverberation environments. If the survey prospect is located in a water depth of between two to twenty (2-20) meters for example, the maximum ranges could vary between fifty to three hundred (50-300) meters for example. In a worse case, transponders would have to be mounted at fifty to one hundred (50-100) meter intervals for example along the cable. A best case might be for example two hundred to three hundred (200-300) meter intervals along the cable.
Large gradients in the speed and sound velocity profile, caused by surface temperature and salinity, will tend to drastically limit the acoustic range. Shadow zones will be caused as the rays are bent downward to the bottom and then reflect upward toward the surface. This bending and reflection will cause many dead or shadow acoustic zones to be present. Acceptable bay cable positioning can be achieved in this environment, even if range data is presently fifty to sixty percent of the time. For this reason, it is extremely advantageous to be able to receive ranges from multiple transponder locations as the source vessel travels its seismic line. Thus, there is a need for a low cost, preferably disposable transponder construction for solving the above-discussed problem.
The following patents are known to Applicant, all of which relating to underwater acoustic devices and/or underwater marker devices.
______________________________________ PATENT ISSUE NO. TITLE DATE ______________________________________ 2,594,702 RETRIEVABLE MARINE MARKER 04/29/52 2,739,296 MARINE MARKER 03/20/56 3,066,325 REPLACEABLE MARINE MARKER 12/04/62 3,125,975 SUBMERGIBLE HULL PROPULSION 03/24/64 AND CONTROL SYSTEMS 3,130,703 PERCUSSION RELEASE HOOK 04/28/64 3,199,070 SONIC CONTROL CIRCUITRY 08/03/65 3,230,500 TRANSMISSION OF TELEPHONY 01/18/66 SPECTRUM OVER VLF CHANNELS 3,287,753 OCEANOGRAPHIC APPARATUS 11/29/66 3,293,676 INSTRUMENT CAPSULE 12/27/66 3,382,514 POSITIVE SCUTTLING BUOY 05/14/68 3,402,687 DEPTH-POSITIONING APPARATUS 09/24/68 FOR UNDERWATER RESEARCH VEHICLES 3,415,317 EQUIPMENT FOR WIRE-LINING 12/10/68 OPERATIONS IN SUBMARINE WELL DRILLINGS 3,487,486 REMOTELY CONTROLLED 01/06/70 UNDERWATER BUOY 3,553,795 HYDRAULIC LATCH 01/12/71 3,638,722 METHOD AND APPARATUS FOR 02/01/72 REENTRY OF SUBSEA WELL- HEADS 3,722,014 RETRIEVABLE BUOY 03/27/73 3,742,440 SYSTEM FOR ACTIVATING A 06/26/73 REMOTE UNDERWATER DEVICE 3,775,736 ACOUSTICAL UNDERWATER 11/27/73 CONTROL APPARATUS 3,793,685 COUPLING APPARATUS FOR THE 02/26/74 MOORING OF BOATS OR THE LIKE 3,889,307 REMOTE-CONTROLLED UNDER- 06/17/75 WATER BUOY 4,024,491 WIRELESS MARINE NAVIGATION- 05/17/77 AL AID SYSTEM 4,097,837 UNDERWATER TRANSPONDER 06/27/78 CALIBRATION ARRANGEMENT 4,110,726 NAVIGATION SYSTEM AND METH- 08/29/78 OD FOR DETERMINING THE POSI- TION OF AN OCEAN MINING SHIP ______________________________________